Photolithography is a key technology in semiconductor fabrication technology. Photolithography is capable of transferring a pattern from a mask to a surface of a silicon wafer to form semiconductor products that meet the design requirements. The photolithography process includes an exposure process, a development process after the exposure process, and an etching process after the development process. In the exposure process, light is irradiated onto the photoresist-coated silicon wafer through regions in the mask where light can pass through, and the photoresist undergoes chemical reactions under the irradiation of light. In the development process, a photolithographic pattern is formed by using the difference in the degree of dissolution of the exposed and unexposed photoresist in the developer, thus the mask pattern is transferred to the photoresist. In the etching process, the silicon wafer is etched based on the photolithographic pattern formed in the photoresist layer. The mask pattern is further transferred to the silicon wafer.
In the semiconductor manufacturing, as the design size continues to decrease, the design size is getting closer to the limits of a photolithography imaging system. The diffraction effect of light becomes more and more obvious, and ultimately resulting in an optical image degradation on the design pattern. The actually formed photolithographic pattern is seriously distorted from the mask pattern, and the actual pattern ultimately formed on the silicon wafer by photolithography is different from the design pattern. This phenomenon is called optical proximity effect (OPE). Sub-resolution assist features, optical proximity correction (OPC), inverse lithography technology (ILT), double patterning, self-aligned double patterning and other technical means are used to improve the photolithography resolution.
Scattering bar (SB) is one of sub-resolution assist features. The scattering bar utilizes auxiliary pattern bars provided around a main feature to improve the photolithographic quality of the main feature. The main feature is an exposable pattern, and the scattering bar is a non-exposable pattern.
However, the conventional method for providing the scattering bar cannot sufficiently determine the scattering bar in each region and improve the stability of a second auxiliary pattern at the same time. The disclosed device structures and methods are directed to solve one or more problems set forth above and other problems in the art.